This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This is a Multicenter double blind, Phase III, placebo controlled clinical trial. SELECT will include 32,400 healthy male participants. Participants will be randomized to receive either 200 ug of selenium, 400 mg of vitamin E, both or placebos for up to 12 years. Accrual is expected to take five years and seven years of follow-up is planned once accrual is completed. The purpose of this study is to compre the effects (good and bad) of the study supplements. The supplements are selenium (L-selenomethionine), vitamin E (alpha-tocopherol), selenium plus vitamin E, and placebo (a pill containing no active substances). We want to see whether the supplements, other than the placebo, can prevent or reduce the occurrence of prostate cancer. The primary objective of SELECT is to assess the effect of selenium and vitamin E on the incidence of prostate cancer diagnozed during routine clinical practice. Secondary objectives include assessing the impact of selenium and vitamin E on the incidence of lung and colon cancer and on cancer specific survival and overall survival. Quality of life, evaluation of molecular and genetic markers of cancer risk, other biomarkers, and measure of nutrient intake will also be assessed.